Method of deoiling wax while supplying supplemental agitation produced by bubbling vaporized solvent through the wax while cooling



Oct.

R. WEEKS 2 METHOD OF DEOILING WAX WHILE SUPPLYING SUPPLEMENTAL AGITATION PRODUCED BY BUBBLING vAPoRIzED soLvENT THROUGH THEv WAX WHILE COOLING Filed April 29, 195s United States Patent O Robert L. Weeks, Scotch Plains, N. J., assignor to Esso Research and Engineering Company, a corporation of Delaware Application April 29, 1955, Serial No. 504,907 4 Claims. (Cl. 196-18) The present invention is concerned with an improved process for the manufacture of waxes. The invention is more particularly concerned with a method for removing the final traces of oil from waxes secured in the refining of hydrocarbon oils. In accordance with the present invention paraffin waxes are segregated from para'in distillates, waxy lubes and the like and then handled in a manner to eliiciently remove oil from the segregated waxes. This is secured by utilizing a solvent in the deoiling operation and using in conjunction with the s01- vent a material selected from the class of pour depressants in combination with auxiliary agitation during chilling. Mechanical agitation may be employed during the chilling step utilizing suitable stirrers, paddles and the like. Another means of providing supplemental or auxiliary agitation is by addition to the chilling zone of compressed vapors, as for example, additional quantities of vaporous solvent. This supplemental agitation in accordance with the present invention is carried out during the chilling cycle; that is, during the removal of heat by the evaporation of the solvent as for instance propane. This application is a continuation-in-part of Serial No. 190,155, now abandoned, filed October 14, 1950.

In the refining of hydrocarbon oils such as petroleum oils, it is known to segregate paraffin waxes from socalled parafiin distillates, waxy lubes and the like. The segregation of these waxes is secured by a number of processes. For example, it is known to chill the selected wax containing fraction in order to secure crystallization of the wax and then to filter the wax crystals from the oil. It is also known to use various dewaxing solvents such as liquid normally gaseous hydrocarbons, such as propane, as well as, other solvents such as methyl-ethyl ketone and the like. In these dewaxing operations, it is also known to use various filter aids and other agents in order to render the dewaxing and filtering operations more efficient.

The wax segregated from the hydrocarbon oil, usually termed slack Wax contains from about 5 to 40% of oil. The oil content and melting point range of this wax may be reduced if desired by means of a distillation operation. The slack wax is then handled usually by sweating in a manner to reduce the oil content to less than about 4% by weight. This, crude scale wax, generally has an oil content of about 2.5% by weight. In order to remove this oil from the wax to produce a refined wax having an oil content below about 0.5%, usually below about 0.3% various procedures have -been proposed and employed. For example, one method is to use a low boiling hydrocarbon solvent such as propane, heat the mixture and then chill the mass and filter. This propane dewaxing operation, however, has not been satisfactory particularly when utilized in the refining of parafiin wax stocks. It should be noted that paraffin Wax refers to waxes obtained from petroleum oils boiling up to about 900 F. Waxes boiling higher than 900 F., which are referred to as amorphous or petrolatum type waxes are inherently easier to dewax and deoil, due to their smaller 2,809,152 Patented Oct. 8, 1957 ICC crystal structure. As pointed out, the deoiling of paraffin waxes with propane is diiiicult because of the tendency for the inherently large wax crystals to interlock and form gels or solid masses in the cooling zone. The higher boiling waxes, i. e. those above 900 F. because of their smaller crystalline structure do not give this difficulty and th;refore can be dewaxed or deoiled without resorting to inventive conditions described below.

Furthermore, in the dewaxing and deoiling of paraffin wax when the gel structure is such that it can be moved in and from the chilling zone, difficulty is experienced in filtering these materials because they tend to form a porous and fluffy wax cake on the filter which cannot be properly discharged from the filter and cannot be washed to a relatively low oil content which is desired.

Thus, the character of the waxy mass formed in the chiller is so gelatinous that it is difficult to remove from the chiller and filter in an efficient manner. One method employed in an attempt to overcome this difficulty is the addition of crystal modifiers such as petrolatum, asphalt and the like. However, when employing aids of this type the filter rates realized were lower than those obtained in the absence of these materials. Furthermore, the addition of relatively large quantities of these materials, such as petrolatum, backed out an equivalent quantity of fresh feed stock; and from a product quality standpoint necessitated subsequent expensive removal operations to segregate the added aids.

It has now been discovered that unexpected desirable results are secured in a wax deoiling operation provided (1) a material of the class of pour depressants is used, (2) in conjunction with propane and (3) in conjunction with auxiliary or supplemental agitation during chilling.

It should be emphasized that the auxiliary o'r supplemental agitation which can be secured by any number of means must be provided during the chilling step, that is, within the cooling zone and is in addition to agitation normally secured by vaporization of the liquefied normally gaseous hydrocarbon solvent which causes chilling to take place. As will be seen hereafter, the agitation provided by the normal vaporization is not adequate to make the process workable.

The solvent deoiling operation should not be confused with solvent dewaxing inasmuch as dewaxing is a much less difficult process. In deoiling operations the charge stock consists almost entirely of wax and at the deoiling temperature essentially all of the charge stock is in the solid state. On the other hand, in dewaxing only a small part of the charge stock is wax and the solids content of the chilled mass, for a given solvent dilution, is much lower than in deoiling. There is, therefore, the problem in deoiling, not present in dewaxing, of handling slurries having a much greater solids content.

The process of the present invention may be more readily understood by reference to the drawing illustrating one embodiment of the same. Referring specifically to the drawing a waxy paraffin distillate is introduced into a dewaxing zone 1 by means of feed line 2. Dewaxing zone 1 may comprise conventional scrape surface chillers and plate and frame presses. The dewaxing zone 1 may also comprise a solvent dewaxing operation wherein solvents such as propane, other light hydrocarbons or ketones such as methylethyl ketone are utilized. The dewaxed oil is removed from dewaxing zone 1 by means of line 3 and handled in any manner desired. The wax fraction known as slack wax is removed from dewaxing zone 1 by means of line 4 and introduced into a wax sweating zone 5.

Usually the slack wax contains from about 15 to 30% by weight of oil. Sweating zone 5 comprises a conventional tank, or pan operation wherein foots oil, other oils and vundesirable low melting point waxes are removed. It is to be understood that the process of the present invention may be employed instead of the conventional sweating zone 5 to secure crude scale wax from slack Wax. A crude scale wax containing less than about 4% of oil usually about 21/2% of oil is removed from zone 5 by means of line 6. This wax is melted in heating zone 7 and introduced into solvent zone 8 wherein it is mixed with a solvent, preferably a liquefiable normally gaseous hydrocarbon such as propane. Generally, the amount of solvent employed is in the range from 2 to 10 volumes of solvent per volume of wax. The solvent is introduced into zone 8 by means of line 9. ln accordance with the present invention before the melted wax is introduced into zone S a small amount of a material selected from the class of pour depressants is added to the melted wax by means of line 25. After thoroughly mixing the solvent, the melted wax and the added pour depressant are removed from zone 8 by means of line 10, further heated at a temperature in the range of 150 to 180 F. in zone 11 to secure complete solution and then cooled to a temperature of about 100 in cooling zone 12. preferably with water, or filtrate, from dewaxing zone 15.

This material is introduced into chilling zone 13 wherein the mass is cooled to a temperature in the range from 30 to -l-60 F. normally to a temperature in the range from about -10 to 20 F. at a rate of from about l to 15 F. per minute. The pressure in chilling zone 13 varies from about 150 to 210 p. s. i. g. at the start of the chilling cycle to from 5 p. s. i. a. to about 50 p. s. i. g. at the end of the chilling cycle. The chilled mass is withdrawn from chilling zone 13 by means of line 14 and introduced into filtering zone 15 wherein the solvent and oil (filtrate) is removed by means of line 16 and the wax cake by means of line 17. Filtering zone 15 may comprise any suitable filtering means such as a rotary drum filter, or its equivalent. The wax removed by means of line 17 may be handled as desired, but is generally passed to a distillation zone 18 where the desired fraction is segregated by means of line 19 and is then preferably percolated over bauxite in zone 20 or another equivalent material for the removal of color bodies. A refined wax is withdrawn by means of line 21. Prior to distilling the wax in zone 18 the remaining solvent is removed from the wax in an intermediate distillation zone not shown on the drawing. Although it is preferred to employ distillation Zone 18 it is to be understood that the wax fraction segregated may be passed directly to Zone 20.

ln accordance with a preferred adaptation of the present invention vaporized propane is withdrawn from zone 13 by means of line 23, and compressed. A pcrticn of this compressed vaporous propane is recycled by means of line 40 to the bottom of zone 13 in order to secure the desired auxiliary agitation. The remaining amount of compressed vaporous propane is passed through a cooling zcne 24 in order to condense the same. This liquid propane ia introduced as a liquid into chilling Zone 13. This liquid rr* pane may be introduced into the system by means of line 9 as hereinbefore described.

The present process is broadly concerned with an improved process for the deoiling of parcfiin wxcs. Th` process generally covers the use of deoiling sclvents` such as liquefiable nrmslly gaseous hydrocarbons, preferably a solvent comprising propane and using in conjunction therewith a material selected from the class of pour depressants. Also, the invention is concerned with the use of auxiliary or supplemental agitation in the chilling zone in conjunction with the use of a material selected from the class of pour depressants. In auto refrigeration the extent of agitation secured by the evaporation of the liquid propane or other solvent is necessarily limited, due to the fact that the chilling rate must not exceed a certain rate. Also to some extent the rate of evaporation of propane is determined by the capacity of the compression equipment available in a particular installation.

Furthermore, in auto-refrigeration wherein propane 0r other solvent is boiling from the mass due to the release by weight.

of pressure on the system, the propane tends to vaporize from the surface thus tending to agitate the surface layers. Thus, the lower layers of the mass remains relatively quiet. For this reason the auxiliary agitation in accordance with the present invention is secured by the introduction of vaporous propane at or near the bottom of the waxy mass.

As mentioned, the wax deoiling solvent may comprise liquefiable normally gaseous hydrocarbons, but preferably comprises liquid propane. The amount of solvent used may vary in the range from about l to 7 volumes of solvent per volume 0f wax. In accordance with a prefrered adaptation of the present invention, it is preferred to use from about 3 to 5 volumes of propane per volume of wax.

The ymaterial employed as heretofore pointed out is selected from the class of materials known as pour depressors. These materials are additives which when added in small concentrations to a lubricating oil will reduce its solidilication point appreciably below its natural solidification point. These materials are described in a publication entitled Lubricating Oil Additives, appearing in the Petroleum Refiner of June 1949, pages 97-102, by V. A. Kalichevsky.

The preferred pour depressants are wax-naphthalene condensation products as described in U. S. Patent 1,815,022 (G. H. B. Davis) which comprises a waxnaphthalene condensation product carried out by means of a Friedel-Crafts catalyst.

Another desirable material for use is one made by esterifying Lorol-B-alcohol with fumarie acid. This is a designation for a mixture of Ca to C18 alcohols, averaging about l2.7 carbon atoms obtained from coconut oils and produced by esterifying the fatty acids followed by hydrogenation. The Lorol-B-fumarate is produced using sulfuric acid as a catalyst in the presence of naphtha at a temperature of 250 F. made by esterifying Lorol-B- alcohol. This material is washed with soda in the presence of sopropanol and with water and the solvent naphtha is removed by distillation. Benzoyl peroxide is added and the fumarate is polymerized at 175 F. under a nitrogen atmosphere for a period of about 15 hours. The polymer is finished by flashing off low boiling fractions to produce a high molecular weight viscous complex which is handled commercially as an oil concentrate.

Another suitable material is manufactured as follows: Lorol-B-alcohol is esteried with maleic anhydride in the presence of a solvent naphtha with a sulfuric acid catalyst at about 250 F. for l2 hours. The mixture is then washed with soda in the presence of sopropanol and then with water, the solvent and naphtha removed and recycled in the esteritication step. The polymer is finished by dashing off low boiling fractions to produce a high molecular weight viscous complex which is handled commercially as an oil concentrate. Vinyl acetate is added to produce a mixture having a proportion of by weight of the Lorol-B maleate and 20% of the vinyl acetate and is diluted with a sulfur free white oil to a concentration of about 70% of esters. Benzoyl peroxide is added and the mixture is polymerized at F. for l2 hours.

The amount of pour depressant employed may vary appreciably but should be in the range from .005 to .3% It is preferred that the amount of active ingredient used be in the range from .O3 to .06% by weight based upon the wax.

The process of the present invention may be more fully appreciated by the following examples illustrating embodiments ofthe same.

EXAMPLE I operations are shown in the following table:

Operations PROPANE DEOILING F PARAFFIN WAX Operation No 1 2 3 4 5 With Added With Agitation With Pour Agitation and Pour Dcprcssant 1 Depressanr 1 But no Agitation Dilution RatioPropane/Oil 3.0 4.5 7.0 4.25 4.25. Supplemental Mechanical Agitation During None None 4,000 llt/hr.2 4,000 lbs./lir.2. None.

Chilling, B./D. Fresh Feed Rate, B./D.:

Parafn Wax 640 484 Petrolatuin Aid 35 (5%) 139 (30%) 0 Wax Production, B./D.:

Gross 503. 456.. Net3 418 267.. Parafiin Wax Quality:

Yield on Parafiin Wax, Vol. Percent 73% 73% 73%. Oil Content, Wt. Percent 0.5 0.35 0.2 0.25 Comments Plant inoperable; Operation Plant limited by Plant inoperable; charge solidified erratic due to chilling capacity charge solidified in chillers. occasional chilldue to high diluin chillers.

erplugging. Untion. Charge soattractive due to lidiiied in chillhigh petrolat-um ers at lower direqiiirement. lution ratio.

1 0.03 vol. percent (active ingredient) of material manufactured as described in U. S. i,815,022. 2 Amount of compressed C; gas to chiller sparges, this agitation augmenting that due to Cv boil-off. 5 Paratlin wax product only. For operations involving use of petrolatuin aid, an added 50 B./D. ol paran was lost during distillation for separaV tion of petrolatum.

Operation 1.-A successful operation under the con- 25 gas to a mass of liquid such as through a spray ring.

ditions as shown in this column was never achieved due to solidication of wax charge in the Chillers. It will be noted that this operation contemplated the use of 5% of petrolatum as a deoiling aid and the use of a low dilution ratio of 3:1.

Operation 2.-As an immediate alternate to the inoperable eonditions given in column l, 'those shown in column 2 were used. An increase in the petrolatum deoiling aid to and an increase in dilution ratio up to 4.5:1 prevented soliditication of the chiller charge. However, this operation was most unattractive in that the use of as much as 30% of petrolatum backed out an equivalent quantity of paraffin wax feed; also, occasional stoppages of the plant chillers were encountered leading to erratic operations. In addition to decreasing the quantity of paraiiin wax feed, the use of petrolatum required its removal from the deoiled wax product by distillation, and substantial additional losses of the deoiled product was encountered in this step.

Operation 3.-By the use of supplemental gas agitation during chilling, the petrolatum deoiling aid was .eliminated, However, it was necessary to increase the dilution ratio to 7:1 and to use 4000 lbs/hr. of propane gas as agitation in order to prevent solidiiication of the Chiller charge. Despite this and faulty operation of the chilling compressors (which limited fresh feed chilling capacity), it was possible to charge 500 B./D. parain Wax feed and obtain a net production of deoiled product of 365 BJD., the highest value obtained up to that point.

Operation 4.-The pour depressant was added as a means by which the dilution ratio of 7: 1 could be reduced and thereby permit the chilling of additional feed. This was actually the case and a reduction to 4.25 :1 was obtained. With this dilution ratio a fresh feed rate of 725 B./D. was found possible and was limited only by the capacity for removing wax from the rotary filters. The net production of deoiled product in this case of 530 B./D. is about double the amount obtained in the operation employing 30% petrolatum.

Operation 5.-Attempts to eliminate agitation gas when using pour depressant additive were made with unsuccessful results. It is evident that both pour depressant and agitation during chilling must be employed.

The amount of supplemental agitation employed will vary appreciably depending upon other operating conditions, for instance the amount of vaporous propane employed per pound of wax processed may vary from .2 lb. of gas to 5 pounds of gas per pound of wax processed. The gaseous propane is preferably added near the bottom of the mass by conventional efdcent methods of adding If mechanical means are used these should be located in such a position so that the entire mass is homogenized. By operating as defined in the chilling zone crystal growth is inhibited and thus sponging, or massing, or interconnection of the crystals is avoided. This avoids the formation of a solid, or gel like structure which cannot be moved and handled in any manner consistent with conventional slurry operations.

What is claimed is:

1. The process for the production of high quality relined parat-liu wax from a crude scale wax obtained by the dewaxing of a petroleum oil boiling up to about 900 F. which comprises adding to said crude wax a solvent comprising liquefied propane and a pour depressant, passing said mixture to a chilling zone and cooling and agitating the same by evaporation of the liquefied propane, further agitating the mass in said chilling zone by withdrawing propane from said zone, compressing at least a portion of said Withdrawn propane and introducing compressed gaseous propane into said chilling zone to provide auxiliary agitation, removing the chilled mass from the chilling zone and separating the propane-containing oil from the wax.

2. The process for the production of a high quality refined parain wax from a crude scale wax obtained by dewaxing of a petroleum oil boiling up to about 900 F. which scale wax is characterized by containing less than about 2.5% by weight of oil which comprises adding to said crude scale wax of from about 3 to about 5 volumes of liquefied propane and from about 0.005 to about 0.3% by weight of a pour depressant, cooling and agitating the mixture in a chilling zone by vaporization of said propane, providing further and supplementary agitation during said cooling step by withdrawing propane from said zone, compressing at least a portion of said withdrawn propane and recycling compressed gaseous propane to said chilling zone, the amount of said gaseous propane being in the range of from 0.2 to 5 pounds of gas per pound of wax processed, and thereafter separating said solvent from the Wax.

3. The process of claim 2 wherein vaporous propane is removed from said chilling zone, compressed and separated into two streams, one of said streams condensed and reintroduced as a liquid into said chilling zone, said other stream passed as a vapor into a lower portion of said chilling zone.

4. The process of claim 3 wherein said pour depressant is a condensation product of chlorinated wax and naphthalene.

(References on following page) References Cited in the le of 4this patent UNITED STATES PATENTS Y OTHER REFERENCES Kalichevsky: Modern Methods of Refining Lubricating Oil, pages 169, 170 andr17n1. A. C. Si. Monograph, Series No. 76, published by Reinhold Publishing Corp., New York, N. Y. (1938). 

1. THE PROCESS FOR THE PRODUCTION OF HIGH QUALITY REFINED PARAFFIN WAX FROM A CRUDE SCALE WAX OBTAINED BY THE DEWAXING OF A PETROLEUM OIL BOILING UP TO ABOUT 900*F. WHICH COMPRISES ADDING TO SAID CRUDE WAX A SOLVENT COMPRISING LIQUEFIED PROPANE AND A POUR DEPRESSANT, PASSING SAID MIXTURE TO A CHILLING ZONE AND COOLING AND AGITATING THE SAME BY EVAPORATION OF THE LIQUEFIED PROPANE, FURTHER AGITATING THE MASS IN SAID CHILLING ZONE BY WITHDRAWING PROPANE FROM SAID ZONE, COMPRESSING AT LEAST A PORTION OF SAID WITHDRAWN PROPANE AND INTRODUCING COMPRESSED GASEOUS PROPANE INTO SAID CHILLING ZONE TO PROVIDE AUXILIARY AGITATION, REMOVING THE CHILLED MASS FROM THE CHILLING ZONE AND SEPARATING THE PROPANE-CONTAINING OIL FROM THE WAX. 